The larval morphology, histological snail response, route of migration of Schistosoma haematobium and S. intercalatum in the molluscan host will be investigated with the object of establishing basic information which will support allied studies by investigators concerned with the in vitro cultivation, susceptibility, metabolism, and specific relationships between S. haematobium and S. intercalatum, and other species of the Schistosoma haematobium complex.